Gender differences in depression and anxiety emerge at about the same time as the pubertal transition, with girls experiencing greater internalizing symptoms than boys. Despite this well-documented finding, we know little about the mechanisms by which the gender gap in internalizing disorders might develop. The current study will add to the literature by investigating an integrated model that incorporates pre-existing vulnerabilities, pubertal development, and social stressors in the prediction of gender differences in adolescent internalizing symptoms. The knowledge gained from the study will be useful for prevention and intervention efforts aimed at reducing the incidence of internalizing disorders among adolescents, and [particularly among adolescent girls. Moreover, the current longitudinal study with six waves of data will add to the extant literature by focusing specifically on peer-related stressors and allowing for an examination of the cumulative effects of pubertal development and social stress between the ages of 12 and 14. Finally, this study will significantly add to the literature by examining the development of internalizing symptoms among a largely low-income, minority population. [unreadable] [unreadable] [unreadable]